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Current, Voltage, Resistance & Ohm’s Law. 13.2 & 13.3. Current. Definition: Flow of electric charge How many electrons pass a given point each second Water Analogy: Rate at which water flows Units: Amps (A) Symbol in Equation: I. Voltage. Definition:
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Current, Voltage, Resistance & Ohm’s Law 13.2 & 13.3
Current • Definition: • Flow of electric charge • How many electrons pass a given point each second • Water Analogy: • Rate at which water flows • Units: • Amps (A) • Symbol in Equation: • I
Voltage • Definition: • Measure of electric potential energy (force or push) • Water Analogy: • Water pressure • Tilt of water pipe • Units: • Volts (V) • Symbol in Equation: • V
Resistance • Definition: • Opposition to the flow of charge • The greater the resistance the less current will flow • Water Analogy: • Rocks in a stream • Nozzle size of water bottle • Units: • Ohms (Ω) • Symbol in Equation: • R
Batteries • Use chemical energy to create a voltage difference, to store electrical energy • Batteries are similar to water towers • Regular batteries can be 1.5 V
Ohm’s Law • Relationship between current, voltage, and resistance V = I x R Voltage = Current x Resistance
Calculate the current in a toaster that has a heating element of 14 ohms when connected to a 120 volt outlet • R = 14Ω • V = 120V • I = ? • V = IR • 120 = I ( 14) • I = 8.57A
What is the resistance of a heat coil on an electric stove if it pulls 4 amps of current when plugged intro a 240 volt outlet? • I = 4A • V = 240V • R = ? • V = IR • 240 = 4(R) • R = 60Ω
Conductor & Insulator • Conductor • Conduct electricity easily (e-free to move) • Low resistance • Most metals • Insulator • Block the flow of current (e-bound tightly to atom) • High resistance • Rubber, glass, wood, plastic
Semiconductor & Resistor • Semiconductor • In-between a conductor and an insulator • Silicon • Resistor • Used to control current • Used in televisions, computers and radios